1) Field of the Invention
The present invention relates generally to electromagnetic propulsion systems, particularly to electromagnetic propulsions systems having separate ballistic guidance and electrical current contact surfaces, and more particularly to railguns having such separated ballistic guidance and current carrying functions.
2) Description of related art including information disclosed under 37 CFR 1.97 and 37 CFR 1.98
Electromagnetic propulsion systems, such as railguns, generally comprise at least one pair of conductive rails surrounding and disposed parallel to the longitudinal axis of a cavity. A power supply connected to the rails causes current to flow when an electrically conductive material (armature) disposed between the rails completes the circuit. The magnetic field formed around the rails applies a Lorentz force to the armature accelerating the armature along the cavity longitudinal axis. A projectile or other object attached to the armature can thus be accelerated and propelled. In addition to the force along the longitudinal axis, there is a lateral force (from the magnetic field) exerted on the rails which can increase the gap between the rails and the armature, possibly resulting in arcing with subsequent damage to the rails and insulator surfaces. The propulsive forces generated in such systems may be used in various kinds of launching systems, weapons systems, and transportation systems (propelling compartments containing animate and/or inanimate objects).
Unlike conventional chemical propellant burning guns, projective velocities in railguns are not limited by propellant gas sound speed. Further, the energy and velocity imparted to a launched projectile may be precisely achieved by controlling the voltage and current provided to the railgun.
Solid armature railguns, to date, have typically used the electrically contacting rail surfaces to also provide ballistic guidance to a projectile component (armature, projectile, and preferably a sabot) as they are propelled down the rails. Eventually, the rail wear becomes excessive and adversely affects the internal ballistics of the railgun. The deteriorated internal ballistic results in a loss of performance (velocity and accuracy): damage to the armature, sabot, and projectile; and further damage to the railgun interior. Plasma armatures are also known in the art, wherein the plasma results from a thin conductive material that is heated rapidly by the current passing through it. The rails, rail support structure, armature, and sabot must work together so that the plasma does not blow past the projectile.
U.S. Pat. No. 4,480,523 discloses an electromagnetic projectile launching system having a plurality of conductive rails distributed azimuthally on the inner surface of a barrel and a plurality of conductive armatures disposed between said conductive rails.
U.S. Pat. No. 5,078,042 discloses an electromagnetic railgun having four conducting rails in a quadra-pole configuration.
U.S. Pat. No. 5,285,763 discloses a railgun having four rails spaced equally and parallel to a predetermined axis of symmetry.
U.S. Pat. No. 5,454,289 discloses a railgun barrel having stacked metallic annular laminations in combination with pre-stressed tension elements to add radial and longitudinal stiffness.
U.S. Pat. No. 6,502,494 discloses a railgun accelerator system powered by alternating current using multiple railguns.